1. Field of the Invention
The present invention relates to a method of measuring a refractive index distribution that measures the refractive index distribution of an object.
2. Description of the Related Art
Japanese Patent Laid-Open No. H08-122210 discloses a method of obtaining a refractive index distribution of an object by measuring a transmissive wavefront while rotating the object at various angles in a state where the object is immersed in a test solution (matching oil) having a refractive index nearly equal to that of the object. Japanese Patent Laid-Open No. 2012-088342 discloses a method of obtaining the refractive index distribution of an object having a high refractive index by measuring the transmissive wavefront while rotating the object at various angles in a state where the object is immersed in two kinds of media having different refractive indices for the object.
In the method of the method disclosed in Japanese Patent Laid-Open No. H08-122210, the matching oil having substantially the same refractive index as that of the object is necessary. However, the matching oil having the high refractive index has a low transmittance and a small signal can only be obtained from a detector, and therefore a measurement accuracy of the object having the high refractive index is deteriorated. Furthermore, the method disclosed in Japanese Patent Laid-Open No. 2012-088342 is assumed that a position or an inclination of the object in rotating the object around an axis perpendicular to an optical axis is previously known. However, an actual shape of the object is different from a design value, and therefore it is difficult to specify the position or the inclination of the object with high accuracy when rotating the object.